ABSTRACT
BACKGROUND: The growth hormone (GH)-insulin-like growth factor (IGF)-SST (SST) axis is involved in diabetic nephropathy (DN). We have recently shown a beneficial effect on diabetic kidney disease markers by the use of a novel somatostatin (SST) analogue (PTR-3173) (S). The purpose of this study is to compare the effects of S with a previously used SST analogue (octreotide) and an ACE inhibitor (ACEi), a standard of care in DN. METHODS: Non-obese diabetic mice (a model of type I diabetes) were treated with either S (DS), octreotide (DO), enalapril (DA), or PTR-3173 and enalapril (DAS group) for 3 weeks. RESULTS: Diabetic renal hypertrophy was blunted in the DS and DO groups only. Serum GH and IGF-I were markedly increased and decreased, respectively, in the D group, a change significantly blunted in DO and DS. Diabetic hyperfitration and albuminuria were blunted in all the four treated diabetic groups. The marked deposition of type IV collagen and PAS material were mildly decreased in DA, but more markedly reduced in DS as well as DO. Diabetic renal laminin accumulation was suppressed in all treated animal groups. No synergistic effect was observed for any parameter in the combination group DAS. CONCLUSION: SST analogues exert beneficial effects in most parameters of diabetic kidney disease to the same extent as the ACEi. Enalapril treatment had no effect on renal hypertrophy and did not cause a significant decrease in mesangial type IV collagen deposition. A synergistic effect of combined SST-ACEi therapy could not be shown in this study.
Subject(s)
Angiotensin-Converting Enzyme Inhibitors/therapeutic use , Diabetic Nephropathies/prevention & control , Somatostatin/analogs & derivatives , Somatostatin/therapeutic use , Animals , Collagen Type IV/metabolism , Diabetes Mellitus, Type 1/physiopathology , Female , Growth Hormone/blood , Immunohistochemistry , Insulin-Like Growth Factor I/metabolism , Kidney Glomerulus/drug effects , Kidney Glomerulus/pathology , Mice , Mice, Inbred NODABSTRACT
BACKGROUND: Nephropathy is the most severe complication of diabetes mellitus. We investigated the effect of exogenous growth hormone (GH) administration on renal function and matrix deposition in the streptozotocin (STZ) model of type I-diabetic rat. METHODS: Adult female STZ-diabetic rats (D), non-diabetic control rats injected with saline (C) and control and diabetic rats injected with bovine GH for 3 months (CGH and DGH, respectively) were used. RESULTS: The usual renal hypertrophy seen in D animals was more pronounced in the DGH group. Creatinine clearance increased only in the D rats, but not in the other groups, including DGH. Albuminuria was observed in the D animals but was significantly elevated in the DGH group. Glomeruli from DGH animals showed more extensive matrix accumulation (manifested as an increase in mesangial/glomerular area ratio). Renal extractable insulin-like growth factor (IGF-I) mRNA was decreased in the D and DGH groups, but renal IGF-I protein was not significantly increased. Renal IGF binding protein-1 was increased in the D groups and further increased in the DGH group, at both the mRNA and protein levels. CONCLUSIONS: GH-treated diabetic rats had less hyperfiltration and more albuminuria, concomitant with more glomerular matrix deposition, when compared with regular diabetic animals. This was associated with a significant increase in renal IGFBP-1, and dissociated from IGF-I changes. Thus, in this model, GH exacerbates the course of diabetic kidney disease.
